If you want to see the future of the portable PC, forget about the MacBook Air. While the fashion-model thin unit (retailing for a flabby $1,799) earns a few admiring glances, it wont prompt a mass movement.

Forget, too, about deluxe supertanker laptops like the HP Pavilion HDX, which fetches $1,999. You can play Warcraft on this machine until your family members forget about you, but it doesnt reflect the hottest growth area in portables.

No, to see where the portable computer industry is headed, take a look at the humble Asus Eee PC. This ultra-compact notebook  a featherweight two pounds  is the Elvis of personal computing. Since bursting on the U.S. market in November 2007 it has rocketed upward in popularity. Zoomed upward. Techies across the country are feeling heart palpitations as they dream of this dwarf-like unit.

Laptop magazine almost blew its dongle over the Asus, breathlessly proclaiming it, Pound for pound, the best value-priced notebook on the planet. (What, not the entire solar system?) CNET took a more tempered approach, yet still deemed it a near perfect choice for a highly portable second or backup laptop.

The Asustek company boldly projects it will ship a robust five million ulta-portable units by the end of 2008, earning it a healthy 10 percent of the global laptop market. That figure looks realistic: in its short time on the market, the Eee PC has moved 350,000 units  without a big bucks ad campaign. (Or a CEO in a cool black turtleneck.)

The Asus portable goes anywhere

I spoke with Debby Lee, an Asustek rep, and she clued me into a surprise the company had about the Eee PC: Originally, it was targeted to housewives, kids, senior citizens  people who have very basic computing needs. But then, a lot of the more savvy computer users started picking it up. Hence the sales trajectory.

All this enthusiasm raises the natural question: Why? Why is the tiny Asus  with its funky 7-inch screen and its downscale 800x480 resolution  prompting so many sweaty palms?

While there may be no fully rational explanation for something thats close to a craze, these factors help the Asus Eee PC 4G:

Price: Yup, It's Cheap

At $399 (or less, based on configuration), the Asus is almost an impulse purchase. Your big bucks can be spent on a serious desktop, crammed full of options, but a quick $400 can be burnt on this throw-it-in-your-backpack unit. In the same way that One Laptop Per Child hoped for a sub-$100 unit, the Asus offers an OLPG deal (One Laptop per Geek).

On the other hand, the ultra-cheap PC market is getting ever more crowded. The Asus isnt alone. In the desktop sector (granted, a different sector than the Eee PC), the $200 PC is popping up all over. The Shuttle, the Mirus PC, the Everex gPC. Every month a new one debuts. These boxes (all Linux machines  its hard to get that cheap with a Windows license) are shockingly low-priced.

And even among laptops, you can find full-fledged unit in the Asuss price range. TigerDirect regularly sells refurbished notebooks for $499. And Lenovo sells a hot 15-inch widescreen notebook for $581.

Cloudbook, another super cheap Linux portable, is expected to hit the glamorous shelves of Wal-Mart by the end of January. And reports say it will have a larger hard drive and a faster chip than the Eee PC.

Bottom line: Its low price helps the Asus, but it is not low price alone that is fueling this portables hit status.